Penetrating a Hole Through a Penny

This is an easy chemistry project that uses common materials. You take a post-1982 penny, score the copper surface to expose the zinc interior, react the zinc with acid, and are left with a hollow copper penny.

Hollow Penny Materials

• post-1982 pennies (the composition of pennies was changed when the copper became more valuable than the currency)
• muriatic acid (from a hardware store) 6M HCl solution (500 mL concentrated HCl solution diluted to 1.00 L distilled or deionized water)
• a disposable plastic container or glass jar
• baking soda
• water
• Goggles
• Glass jar

Make Hollow Pennies:

• You need to expose the interior of the pennies. You can score the edge of the pennies with a file or snip them with wire cutters, but I think the easiest way to expose the zinc is to rub the edge of each penny along a brick or concrete block. You could use sandpaper, if it's available. Use whatever is handy to expose some of the zinc (don't go all the way around the coin). If you can see silver metal under the copper of the penny, you're ready to proceed to the next step.
• It's best to do this step outdoors or under a fume hood, wearing gloves and protective eye wear. Read the safety precautions on the muriatic acid container. Basically, this is hydrochloric acid. Treat it with respect. Place the pennies in your container. Pour a little muriatic acid over the pennies so that they are covered. Bubbles will start to form immediately. Set the container somewhere where it will be safe from spills, children, and pets. Let the reaction proceed for about 6 hours.
• Carefully pour off the muriatic acid. You can wash it down a drain, providing you use a lot of water.
• Fill the container with water. Add a little baking soda to neutralize the residual acid.
• Examine your penny. The hollow penny will be a fragile copper foil.

Questions that I might need to think about:

1. How many hours, or days does the penny needs to take to lose its color?
2. What does Muriatic Acid and Zinc have to do with chemical reaction?

Result:

First, I left my penny in for about 6 hours or more in the container in which it contained muriatic acid. When I looked at the penny. There was color, but the zinc that was inside the penny has disappeared, meaning that it would have reacted with the acid, by either melting it or evaporating it with hot temperature, because I show some bubbles coming out. I cleaned the penny with the Baking soda, neutralizing the residual acid. Then, I exposed the opposite side of the penny. (the time I tried to expose the interior of the penny, it was only a small bit.) I put penny and muriatic acid again into the container, and have left it probably over 3 days. It was an amazing experiment. The penny has lost its copper color, and became grey, and it was so fragile, that I could almost crush it into pieces. I really had to be careful.

Beaker :34.03g
Beaker+salt(salt is the material that was left over after heating up the muriatic acid, which the 3 day long penny was in it.): 35.50g
Salt: 1.47g
The salt is guessed and believed as "zinc chloride" but I am not quite sure yet.

It is also believed that when you mix Muriatic Acid (hydrochloric acid) and zinc together, you got hydrogen gas.Any average joe can write down a simple UNBALANCED chemical equation.
The proper equation would be 2HCl+Zn--->H2+ZnCl2
notice the number 2 infront of the HCl.

Second of all Hydrochloric Acid does not make Chlorine gas when reaction with chemicals like zinc. It makes hydrogen gas and zinc chloride. The only wat to make HCl give off chlorine is reduce the oxidation state of the chlorine with a strong oxidizer like KMnO4.

Assume that Zn is 65g with H is 1g. Also Cl as in 35g.
The equation 2Zn + 2HCl = H2 + 2ZnCl
If 2Zn is 65g then 2ZnCl is 98g.
98/65 is approximately 1.5
This means that 2ZnCl is 1.5times heavier than 2Zn, concluding with Cl being 1.5times of 35 so 52.5g.
Zn + 2HCl --->H2 + ZnCl2
(s)=solid
(l)=liquid
(g)=gas
(ag)='aqueous'-aqua
You can substitude this variables into the equation.
Zn (s) + 2HCl(ag) ---> H2(g) + ZnCl2(ag)
Pictures of HCl

HCl

Other Experiment!

Zinc Plated Penny

Materials:

• 1 piece of of zinc. An easy source of zinc is the shell of a carbon-zinc battery (do not use alkaline or rechargeable battery.) An adult should cut up the shell, remove the black glop, and clean the zinc, (wear plastic gloves). You can also sand off the thin layer f copper on a penny (1983 or newer) to reveal a zinc core.
• 1 penny, preferable a shiny one or you can remove the tarnish by soaking in vinegar mixed with some table salt.
• 250ml Vinegar (about 1 cup)
• 25g Epsom Salt (5tsp)
• 30g Sugar (6tsp)
• 1 glass bowl

• 1 glob toothpaste and toothbrush

• 1 "D" size battery (1.5v)

• 2 wires to make the electrical connections

• 2 plastic gloves

Procedures:

• 1. Pour the vinegar into the glass bowl. Put the zinc into the vinegar and let it sit for several hours to dissolve some of the zinc.
• 2. Add the Epsom salt and sugar. Stir well to dissolve.
• 3. Use the toothpaste and brush to polish the penny until it's shiny and then rinse well with water. Wear plastic gloves so you do not get fingerprints or other soils on the penny after cleaning.
• 4. Connect the positive terminal of the battery to the zinc and the negative terminal to the penny using the wires and place them into the vinegar solution. Do not let them touch!
• 5. Within few minutes, you should get a silvery coating on the penny.

TIP: If your coating is dull grey instead of silver, make sure you cleaned the penny really well. You can also try using the toothbrush and toothpaste to polish it.
TRY THIS! Turn your "silver" penny "gold". Place it in a 350 oF even for about 15 minutes. The zinc mixes or "alloys" with the copper and forms brass.

http://www.lanl.gov/orgs/pa/newsbulletin/2005/03/02/ZincPlatedPenny.pdf